Attempt scroll restoration anytime viewport size changes

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index c9c429ac81677e8f703528ccb03a89e71f526610..17ad78f34544828492c8721e5e5029a434f82f57 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -406,8 +406,11 @@ void FrameView::setFrameRect(const IntRect& newRect)
 
     viewportSizeChanged(newRect.width() != oldRect.width(), newRect.height() != oldRect.height());
 
-    if (oldRect.size() != newRect.size() && m_frame->isMainFrame())
-        page()->frameHost().visualViewport().mainFrameDidChangeSize();
+    if (oldRect.size() != newRect.size()) {
+        if (m_frame->isMainFrame())
+            page()->frameHost().visualViewport().mainFrameDidChangeSize();

[Nate Chapin, 2015/08/24 17:18:18]

Nit: this line should be m_frame->host() instead of page()->frameHost(). Would
you mind updating it while you're here?

[majidvp, 2015/08/25 19:12:42]

Done.

+        frame().loader().restoreScrollPositionAndViewState();
+    }
 }
 
 Page* FrameView::page() const
@@ -509,20 +512,7 @@ void FrameView::setContentsSize(const IntSize& size)
     updateScrollableAreaSet();
 
     page->chromeClient().contentsSizeChanged(m_frame.get(), size);
-}
-
-IntPoint FrameView::clampOffsetAtScale(const IntPoint& offset, float scale) const
-{
-    IntPoint maxScrollExtent(contentsSize().width() - scrollOrigin().x(), contentsSize().height() - scrollOrigin().y());
-    FloatSize scaledSize = visibleContentSize();
-    if (scale)
-        scaledSize.scale(1 / scale);
-
-    IntPoint clampedOffset = offset;
-    clampedOffset = clampedOffset.shrunkTo(maxScrollExtent - expandedIntSize(scaledSize));
-    clampedOffset = clampedOffset.expandedTo(-scrollOrigin());
-
-    return clampedOffset;
+    frame().loader().restoreScrollPositionAndViewState();
 }
 
 void FrameView::adjustViewSize()